According to a group of researchers headed by Prof Asa Barber of the University of Portsmouth, UK, the teeth of limpets – small aquatic snails – are the strongest biological material yet discovered.
Scanning electron microscope image of limpet teeth. Image credit: Asa H. Barber et al / University of Portsmouth.
“Until now we thought that spider silk was the strongest biological material because of its super-strength and potential applications in everything from bullet-proof vests to computer electronics but now we have discovered that limpet teeth exhibit a strength that is potentially higher,” said Prof Barber, who is the first author of the paper reporting the results in the journal Interface.
Prof Barber and his colleagues examined the small-scale mechanical behavior of teeth from limpets using a technique called atomic force microscopy.
They found that the teeth contain a hard mineral known as goethite, which forms in the limpet as it grows.
“Limpets need high strength teeth to rasp over rock surfaces and remove algae for feeding when the tide is in,” Prof Barber said.
“We discovered that the fibers of goethite are just the right size to make up a resilient composite structure.”
He added: “this discovery means that the fibrous structures found in limpet teeth could be mimicked and used in high-performance engineering applications such as Formula 1 racing cars, the hulls of boats and aircraft structures.”
“Engineers are always interested in making these structures stronger to improve their performance or lighter so they use less material.”
The scientists also discovered that limpet teeth are the same strength no matter what the size.
“Generally a big structure has lots of flaws and can break more easily than a smaller structure, which has fewer flaws and is stronger. The problem is that most structures have to be fairly big so they’re weaker than we would like,” Prof Barber explained.
“Limpet teeth break this rule as their strength is the same no matter what the size.”
The material was almost 100 times thinner than the diameter of a human hair so the techniques used to break such a sample have only just been developed.
The testing methods were important as we needed to break the limpet tooth. The whole tooth is slightly less than a millimeter long but is curved, so the strength is dependent on both the shape of the tooth and the material,” Prof Barber said.
“We wanted to understand the material strength only so we had to cut out a smaller volume of material out of the curved tooth structure.”
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Asa H. Barber et al. Extreme strength observed in limpet teeth. Interface, published online February 18, 2015; doi: 10.1098/rsif.2014.1326
